Depending on the gain of the preamp and how the attenuator ( volume control ) is designed, some amps may max out at as little as 9 or 10 o'clock ( tube pre driving ss amp ), 1 o'clock ( ss pre driving ss amp ) or not at all ( passive line section into any amp ). As such, i would not worry about where the volume control is set at, just so long as it can play as loud as you like and it is still clean and well defined.
I think Chazzbo is asking if the amp stays "cohesive" and maintains its' performance as volume is increased. Some amps sound good until they are pushed above a specific threshold. This does not necessarily mean that they are clipping, only that they sound best within a limited power range. I have heard amps that lost their coherence, stability, soundstage, definition, etc... as volume was increased. As such, only those that are pretty familiar with the amp can answer that question. Sean